1. Field of the Invention
This invention relates to a triggering device for a vehicle occupant safety apparatus such as an air-bag apparatus or a vehicle safety-belt pretensioner (tightener).
2. Description of the Prior Art
U.S. Pat. No. 5,107,245 discloses a control arrangement for the occupant restraint system of an automotive vehicle which includes an acceleration pickup for sensing deceleration of the vehicle and providing an acceleration signal. A trip device is in the occupant restraint system. A microcomputer processes the acceleration signal. The microcomputer supplies one or more trip signals to the trip device when the result of processing of the acceleration signal fulfills a criterion for activation of the occupant restraint system. A monitoring circuit external to the microcomputer includes an associated stable oscillator providing a reference signal. The monitoring circuit serves to monitor, as to correct frequency by comparison with the reference signal, a check signal derived from a clock signal of the microcomputer. The monitoring circuit produces an enable signal when the check signal has the correct frequency. The monitoring circuit activates an indicating means when the check signal is found to be incorrect. The monitoring circuit prevents the supply of the trip signal to the trip device in response to the disappearance of the enable signal.
U.S. Pat. No. 5,359,515 corresponding to Japanese published PCT application 4-506495 discloses a vehicle occupant safety system which includes a sensor device having at least two sensors, and a processing device having at least two processing circuits for the respective sensor signals. The vehicle occupant safety system in U.S. Pat. No. 5,359,515 further includes a computing system and a trigger circuit each having at least two stages for a safety device. For providing a high degree of safety with relatively low costs, the computing system is constructed as a single-computer system in such a way that it processes the data of the two processing circuits in two programs with staggered timing with respect to one another.
Japanese published unexamined patent application 5-69791 discloses a side-crash sensing system for automotive side air-bag devices in which an air-bag trigger component is controlled in response to the output signals of plural acceleration sensors.